Many attempts have been made to prepare hybrid polymer dispersions, in particular alkyd-vinyl hybrid polymer dispersions, aiming to achieve an ideal balance of the best properties of each of the polymers combined in the hybrid polymer. Alkyd emulsions and vinyl polymer dispersions, made by means of emulsion polymerization, are the two most common waterborne technologies used in the coating industry. Coatings based on alkyd emulsions exhibit advantages over those based on vinyl polymer dispersions in terms of gloss, brush-ability, open time, flow and levelling, hiding per coat, mar resistance, sand-ability, and adhesion. Advantages of vinyl polymer dispersions over alkyd emulsions include quick drying, durability, non-yellowing, non-embrittling, and non-chalking (pigment release by degradation of the binder).
In addition to the advantages described above for alkyds, coatings based on alkyd-modified hybrid dispersions have improved film forming properties due to the presence of alkyd moieties, which typically have a low glass transition temperature (Tg). However, alkyd resins and vinyl polymers are incompatible, and hence prone to suffer phase segregation that results in haziness and lower gloss. Compatibility can be improved by enhancing grafting of the vinyl polymer onto the alkyd resin but this causes the loss of the unsaturated groups of the alkyd, which results in the deterioration of the auto-oxidation properties of the alkyd. The presence of the phase-separated alkyd also results in critical problems, such as soft films (causing dirt pick-up and poor block resistance) and yellowing. High residual monomer content is a threat to the environment and health and is strictly regulated. Furthermore, during the addition polymerisation, unsaturated groups on the alkyd are lost, resulting in the deterioration of the auto-oxidation properties of the alkyd. The known hybrids also have an undesirably low open time, defined as the period of time during which corrections can be made in the wet paint film without leaving brush marks.